; evaluate (load "load-rule-sys") before loading this file into Lisp

;;; These rules illustrate the use of the "Lisp escape" feature.

(define-rules
  (if   (temperature ?x ?y)
        (lisp-eval (>= '?y 99))           ; quote not necessary here
   then (has-fever ?x))
  (if   (parent ?x ?y)
        (parent ?x ?z)
        (lisp-eval (not (eql '?y '?z)))   ; but it is necessary here
   then (sibling ?y ?z))
  (if   (parent ?x ?y)
        (has-fever ?y)
   then (worries-about ?x ?y))
  )

(define-facts
  (temperature john 98.6)
  (temperature sally 101)
  (parent dorothy tom)
  (parent dorothy sally)
  )